Disruptive behavior disorders are characterized by antisocial, aggressive behaviors. Externalizing problems are the most commonly diagnosed mental health problems of childhood. They tend to be stable over time, resistant to treatment, and linked to psychiatric disorders in adolescence and adulthood. Early onset aggression is a precursor of life-course persistent antisocial behavior. Little is known, however, about constitutional and environmental factors, and their interactions, that contribute to different developmental outcomes. Eighty-two 4-5 year-old children at low, moderate or high risk for later disruptive behavior disorders (based on initial levels of externalizing problems), have been studied at three subsequent time points; 6-7, 8-10, and 12-13 years. Social, emotional, cognitive, and physiological areas of child functioning are examined, in conjunction with socialization experiences. The goal is to identify key factors that contribute to continuity and change over time in young children's behavioral problems. The problems of preschool children studied here have shown marked stability over time, indicating their chronic, pervasive nature. Previous reports on this sample described adaptive child-rearing practices and child characteristics that contributed to initial decreases in behavior problems for some of the children. Child and parent risk factors also were identified that contributed to the maintenance of problems for other children. Current projects focus on followup of these children into early adolescence. Both early and concurrent problems have been found to predict negative affect and physiological reactivity to social stress in adolescence. The stability of problems identified at earlier time points continues into adolescence. There is a marked increase in the number of participants who receive psychiatric diagnoses, with comorbidity often present (e.g. adolescents who have internalizing (anxiety, depression) as well as externalizing (oppositional, antisocial) problems. Because disruptive behavior problems are more likely to be comorbid with anxiety and depression in girls than boys, this may lead to later sex differences in forms of psychopathology. We have identified early sex differences in coping that may place girls at greater risk for internalizing problems.